shower



Jan. 31, 1956 E. e. SHOWER METHOD OF MAKING CONTACT POINTS Filed July 2, 1949 INVENTOR E. G. SHOWER A TTORNEV United States. Patent Ofiice 2,732,614 Patented Jan. 31, 1956 2,732,614 METHOD OF MAKING CONTACT POINTS Application July 2, 1949, Serial No. 102,749 3 Claims. (Cl. 29-15555) This invention relates to the manufacture of signal translating devices and more particularly to methods of making contact point structures for such devices of the general type disclosed in the application, Serial No. 33,466, filed June 17, 1948, of J. Bardeen and W. H. Brattain, now Patent No. 2,524,035, issued October 3, 1950.

One form of signal translating device of the type disclosed in the above-identified application comprises a body or wafer of semiconductive material, such as germanium or silicon, and a pair of point contacts bearing against one face of the body or wafer.

' The performance characteristics of such devices are markedly dependent upon the relation of the contact points. Maintenance of prescribed spacing and orientation of the points heretofore has been very difficult because of the requisite small size, and consequent fragility, of the contact wires. For example, in one specific structure the points are of five-mil wire and have enantiomorphically related chisel points spaced from each other of the order of two mils bearing against the wafer surface. Any substantial variation in the spacing or orientation of the points materially alters the operating characteristics of the translating device.

One general object of this invention is to facilitate the manufacture of signal translating devices of the type above described. More specifically, objects of this invention are to expedite the attainment of a prescribed space relation and orientation of the contact points and to facilitate the manufacture of devices in quantity and having substantially the same operating characteristics.

In accordance with one broad feature of this invention, in the manufacture of the contact point structure, the contact points are fixedly maintained in preassigned relation while the points are formed to the desired shape and the contacts are mounted in the device. In accordance with a more specific feature of this invention, the contacts are formed by embedding a folded, for example U-shaped, contact wire in a body of a material, such as a plastic, which may be dissolved without affecting the wire, and machining the body and wire to form enantiomorphically related chisel points on the arms of the folded wire. two arms may then be afiixed to rigid leading-in conductors :and the body material removed .The above-noted and other features of this invention will be understood more clearly and lowing detailed description with reference to the accompanying drawing in which: 4

Fig. 1 is an elevational view of a signal translating device of the type to which this invention pertains, a portion of the housing being broken away to show the internal structure more clearly;

'Fig. 2 shows preliminary steps in preparing the contactwires forpointing according to one embodiment of this invention;

Fig. 3 shows the wires of. Fig. after they have been milled and polished to chisel points;

Fig. 4 shows the wires of Fig. 2 mounted on the lead-in conductors of the translating device of Fig. 1;

Fig. 5 shows an alternative method of mounting the wires of Fig. 2 on the lead-in conductors of the device of Fig. 1;

Fig. 6 shows unpointed contact wires mounted on lead-in conductors of the device of Fig. 1; and

Fig. 7 depicts apparatus for forming the chisel points on the mounted wires of Fig. 6.

Referring now to the drawings, the translating device mounted a conductive plug 11 carrying a body of semiconductive material 12 such as silicon or germanium connected thereto by a low resistance ohmic connection formed for example, by copper plating one surface of the body and soldering it to the plug. An insulating plug 1.4 having a pair of lead-in conductors 15 and 16 passing through it is mounted in the other end of the shell 10 so that the points 17 and 18 of the wires 19 and 20 engage the surface of the semiconductive body sufficiently close together for mutual influence. These contact Wires 19 and 20 are of small diameter and of short length and therefore are difficult to handle and sharpen, the exemplary device of Fig. 1 having a shell less than 0.5 inch in length and employing 5-rnil diameter Phosphor-bronze contact wires. The final assembly is shown in Fig. 1 requires that the chisel faces be so oriented that the extensions of their planes intersect on a line parallel to the surface of the semiconductive body 12 and coinciding with a line normal to that surface and centrally located between the contacts possible a nominal spacing of the order of two mils between contacts on the semiconductor surface. In addition, the line including the two contact points must be essentially parallel to the semiconductor surface before contact is made so as to insure that after assembly the pressure exerted against the face of the semiconductors are approximately equal.

In order to economically handle, sharpen and mount contacts of this nature, special techniques are necessary. One method in accordance with this invention comprises winding the contact wire 22 which may be of Phosphorbronze, onto a plastic mandrel 23 of polymethyl methacrylate or some similar material the width and thickness of which are such that the length of the wires forming final assembly; The turns or portions of each turn are then embedded in a plastic matrix 24, for example by cementing a plastic plate 25 on each side of the winding on mandrel 23 and coalescing the mass by the application of pressure and heat. One side of the assembly ineluding a portion of the winding is then milled to a The above steps produce a series of U-shaped wires having the ends of the legs of the U formed with enantiomorphically related chisel points 21.

be exposed so that the legs of the loop may be conveniently welded to the lead-in 15 and 16.

The plastic which remains adjacent the points 21 in the second suggested method, as disclosed in Fig. 5, serves to protect the points while they are being mounted on the lead-in connectors and is dissolved away prior to the final assembly of the unit.

As an alternative to dissolving away a portion of the embedding matrix, the wire 22 may be wound on the matrix with a long enough loop protruding from the plastic to permit welding before dissolving the plastic. This also protects the points until after the welding operation is completed.

Another embodiment of the method of forming a pair of chisel points on contact wires is disclosed in Figs. 6 and 7. In this method, two wires 27 and 28 of somewhat greater length than required in the final assembly are welded so they are parallel to the ends of the lead-in connectors 15 and 16 as shown in Fig. 6. The plug assembly is then inserted into a tool 35, Fig. 7, consisting of a pair of hard steel jaws 29 of the proper shape and disposition to clip off the ends of the wires 27 and 28 and at the same time form chisel-type faces 21 on their ends. A mandrel 30 having a thickness equal to the separation between the contact wires 27 and 28 is positioned between the hard steel jaws 29 so that the plug assembly may be mounted in the tool with the contact wires 27 and 28 on opposite sides of the mandrel 30 and so positioned therein that the jaws 29 will close on the wires and the mandrel at such a point that the length of the contact wires will be as desired in the finished assembly. The tool 35 as disclosed in Fig. 7 is merely an illustrative embodiment, the shearing jaws 29 being mounted on the ends of rods 31 and arranged for manual operation by applying pressure to the knobs 32 on the ends of the rods, the springs 33 causing the jaws to reopen when the pressure is released.

Prior to mounting the plug 14 in the shell the contact wires are bent so that the point bearing ends are substantially parallel to the axis of the plug and the intermediate portions are formed with C-shaped bends which provide them with the proper resilience to give the desired contact pressure between the points 17 and 18 and the surface of the semiconductor 12 in the final assembly. In the first embodiment the bending operation is performed after the points have been formed and polished. However, in the second embodiment where the points are clipped, the operation may be performed either before or after the forming of the C-shaped bends in the wires. In this case the latter is preferred since it eliminates to a large extent the possible disturbance of the relationship between the points by the bending operation.

The final operation prior to assembly into the cartridge or shell 10 is a bending of the leads inward to obtain the nominal 2-mil spacing between the points.

The unit is then assembled by forcing the plug 14 supporting the point assembly a predetermined distance into the shell 10. The plug 11 is forced into the opposite end of the shell so that the semiconductive wafer 12 and the contacts 17 and 18 are aligned axially of the shell. The plug 11 is advanced until the points 21 of contacts 17 and 18 engage the wafer 12, this may be detected by using an electrical test circuit. When the points have made contact the plug is advanced a slight distance further thereby placing the contacts under compression and preventing disturbance of their relative positions due to mechanical shocks, expansion of the elements under thermal changes and the like.

What is claimed is:

1. The method of making a translating device having a pair of closely spaced electrodes with enantiomorphically related chisel points which comprises first securing a pair of spaced lead-in conductors to a mounting element of the device, securing an electrode to each conductor, bending the electrodes to form spring sections therein and to space the ends to the approximate dimension desired in the finished device, inserting a mandrel between the ends of the secured electrodes, shearing each electrode end portion to a chisel faced form which is enantiomorphically related to the chisel faced form on its associated electrode by closing a jaw on each electrode end and against said mandrel, maintaining the rotational orientation of each sheared electrode about its axis when said electrodes are incorporated in the device, and incorporating the assemblage comprising said mounting element, said conductors and said electrodes in said device by securing said mounting element thereto.

2. The method of making a translating device having a pair of closely spaced electrodes with enantiomorphically related chisel points which comprises first securing a pair of spaced lead-in conductors to a mounting element of the device, securing an electrode to each conductor, bending the electrodes to form spring sections therein and to space the ends to the approximate dimension desired in the finished device, positioning a spacing means between the ends of the secured electrodes, machining each electrode end portion in a separate plane to form a face thereon which is enantiomorphically related to the face.

machined on its associated electrode while a portion of the electrode is maintained against said spacing means, maintaining the rotational orientation of each sheared electrode about its axis when said electrodes are incorporated in the device, and incorporating the assemblage comprising said mounting element, said conductors and said electrodes in said device by securing said mounting element thereto.

3. The method of making a translating device having a pair of closely spaced electrodes with enantiomorphically related chisel points which comprises first securing a pair of spaced lead-in conductors to a mounting element of the device, securing a straight electrode to each conductor in parallel relationship with the electrode on the adjacent connector, inserting a mandrel between the ends of the secured electrodes, shearing each electrode end portion to a chisel faced form which is enantiomorphically related to the chisel faced form on its associated electrode while it is maintained against said mandrel, bending the electrodes to form spring sections therein, maintaining the rotational orientation of each sheared electrode about its axis when said electrodes are incorporated in the device, and incorporating the assemblage comprising said mounting element, said conductors and said electrodes in said device by securing said mounting element thereto.

References Cited in the file of this patent UNITED STATES PATENTS 1,280,892 Steenstrup Oct. 8, 1918 1,331,030 Ryan Feb. 17, 1920 1,551,342 Steenstrup Aug. 25, 1925 1,605,688 Olin Nov. 2, 1926 2,054,335 Nelson Sept. 15, 1936 2,113,674 Brickman Apr. 12, 1938 2,156,660 Van Geel May 2, 1939 2,182,968 Lunsford Dec. 12, 1939 2,321,071 Ehrhardt June 8, 1943 2,339,402 Herzog Ian. 18, 1944 2,429,222 Ehrhardt Oct. 21, 1947 2,430,028 Pfann Nov. 4, 1947 2,446,672 Sirp Aug. 10, 1948 2,459,787 Bloom Jan. 25, 1949 2,538,593 Rose Jan. 16, 1951 2,595,497 Webster May 6, 1952 2,606,960 Little Aug. 12, 1952 2,609,427 Stelmak Sept. 2, 1952 2,615,965 Amico Oct. 28, 1952 2,632,042 Fritchett Mar. 17, 1953 FOREIGN PATENTS 595,601 Great Britain Dec. 10, 1947 OTHER REFERENCES Electronics, September 1948, pages 68-71. 

1. THE METHOD OF MAKING A TRANSLATING DEVICE HAVING A PAIR OF CLOSELY SPACED ELECTRODES WITH ENANTIOMORPHICALLY RELATED CHISEL POINTS WHICH COMPRISES FIRST SECURING A PAIR OF SPACED LEAD-IN CONDUCTORS TO A MOUNTING ELEMENT OF THE DEVICE, SECURING AN ELECTRODE TO EACH CONDUCTOR, BENDING THE ELECTRODES TO FORM SPRING SECTIONS THEREIN AND TO SPACE THE ENDS TO THE ZPPROXIMATE DIMENSION DESIRED IN THE FINISHED DEVICE, INSERTING A MANDREL BETWEEN THE ENDS OF THE SECURED ELECTRODES, SHEARING EACH ELECTRODE END PORTION TO A CHISEL FACED FORM WHICH IS ENANTIOMORPHICALLY RELATED TO THE CHISEL FACED FORM ON ITS ASSOCIATED ELECTRODE BY CLOSING A JAW ON EACH ELECTRODE END AND AGAINST SAID 